From the way it reads
The Uboats will have that much fuel left to operate IN the region
In other words journey to and from removed from equation and thats whats left
Of course it has to be guess work figures as weather/engine condition and usage and evasive tactics employed on either route would all impact on fuel reserves
And I dont think they had at that time actually ran a boat to those locations
And of course you dont know whether that includes refuelling
